| Desertification is the major problem of the people's livelihood at present, which threat to the national ecological safety, restricts the social and economic sustainable development seriously. It is important and urgent to combat and prevent desertification. The novel and eco-friendly sand-fixation material need strong cohesive action to make loose sand bond together, form a high bond strength consolidation layer. Meanwhile, it also need certain water absorption and water retention ability, to reduce evaporation and water storage, ensure the water supply of psammophyte in the growth process, and create a good condition for plant growth. The development of organic-inorganic sand-fixation and water-retaining mineral based on the natural polymer (sodium alginate, xanthan gum, etc.) and clay could not only reach the purpose of the windbreak, sand-fixation and restore vegetation, but also avoid pollution of the hard-degradable polymer materials in desert areas.Based on the above research purpose, in this paper, the PVA-g-PAA/APT NaAlg-g-PAA/organo-loess, XG-g-laterite/PAA composites were prepared by graft polymerization in aqueous solution for used as superabsorbent and sand-fixation material. The influence of various factors on the composite properties and application performance were systematically investigated. The structure and morphology of the composites were also be characterized. The main work is as follows:1. A novel, low-cost and eco-friendly organic-inorganic composite superabsorbent is successfully prepared in aqueous solution by graft copolymerization of partially neutralized acrylic acid (AA), poly(vinyl alcohol) (PVA) and attapulgite (APT) using ammonium persulfate (APS) as an initiator and N, N-methylenebisacrylamide (MBA) as a crosslinker. The structure and morphology of the composite superabsorbent are characterized by means of FTIR, XRD, FE-SEM and TEM. The effects of APT content which can affect the water absorbency and the pH, ionic surfactants and different saline solution which can affect swelling capabilities of the composite superabsorbent are also investigated. The results show the composite superabsorbent give the best absorption up to 680 g g-1 and 53 g g-1 in distilled water and 0.9 wt% NaCl solution, high water absorbency over a wide pH range of 4-10, high swelling capacity in anionic surfactant (SDBS) than that of cationic (CTAB) solution, which makes it promising for potential applications in modern agriculture and horticulture. On the other hand, the composite superabsorbent can be used for removing multivalent metal ions.2. A novel superabsorbent composite with high swelling properties is synthesized by grafted co-polymerization partially neutralized acrylic acid (AA) onto the sodium alginate (NaAlg) backbone in the presence of organo-loess. The FTIR spectra, XRD patterns and SEM micrographs prove that the AA monomers are grafted onto the NaAlg backbone, and the organo-loess disperse in the polymer matrix which improves porous structure can be further evidenced by the element mapping. TGA and DSC results indicate that the incorporation of loess enhances the thermal stability of superabsorbent. Swelling results confirm that the proper amount of organo-loess in the superabsorbent can enhance swelling capability and salt-resistant performance. The maximum equilibrium water absorbency of the superabsorbent composite incorporated with 10 wt% rgano-loess in distilled water and 0.9 wt% NaCl aqueous solution are 656 g g-1 and 69 g g-1, respectively. Furthermore, the superabsorbent composite exhibits good buffer ability to external pH in the range from 4 to 10 and water retention ability. According to the performances of the eco-friendly superabsorbent composite, it can be used as a promising candidate for applications in various fields.3. A novel and eco-friendly xanthan gum-g-poly(acrylic acid)/laterite (XG-g-PAA/laterite) organic-inorganic composite polymer used as chemical sand-fixing agent (CSFA) was successfully prepared by grafted co-polymerization of natural xanthan gum (XG), partially neutralized acrylic acid (NaA) and laterite in solution. FTIR spectra confirmed that NaA had been grafted onto XG chains and the-OH groups of laterite participated in polymerization reaction. The influence of content of CSFA on sand-fixing effect was investigated and the results of aging test indicated that the CSFA had the remarkable water-resistance, heat resistance, anti-freeze thaw and anti-ultraviolet aging performances, which could meet the requirement of application in the harsh desert environment. Moreover, it also showed the excellent water-retaining and anti-evaporation properties. |
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